1. Field of the Invention
The present invention generally relates to a multi-hop wireless backhaul network. More particularly, the present invention relates to a call admission controller and a call admission control method thereof for a multi-hop wireless backhaul network and a multi-hop wireless backhaul network thereof.
2. Description of Related Art
The technical development of wireless local area networks has gradually matured such that applications thereof have extended from being originally in small indoor areas to extensive outdoor environments. Since it is both time consuming and costly to lay out wired backhaul networks, wireless backhaul networks adopting wireless area networks as the technical background have gradually become an advantageous alternative to the wired backhaul networks. Coverage of a wireless area network is approximately 100 m. In order to achieve a wide coverage of the backhaul network, the wireless backhaul network adopts a method of using relay nodes to transfer with multi-hops and connect to a wired gateway and eventually to the Internet. In such a wireless backhaul network, a connection point which provides both access and relay functions is referred to as a relay node through which communication is transferred to an admission point, and the admission point is referred to as a gateway. The connection point and admission point mentioned below are referred to as a relay node and a gateway.
When laying out a wireless backhaul network in an outdoor environment, for the purpose of convenience in management of electrical interference and traffic flow, the most commonly adopted network topology is a chain topology. In the multi-hop wireless backhaul network, not only can data be transferred between relay nodes in a wireless manner but users within coverage of a relay node itself can also connect to the relay node in a wireless manner. The two wireless communication manners use different frequency bands and transmission interfaces to avoid causing tremendous interference. For example, connection between relay nodes or between a relay node and a gateway uses IEEE 802.11a protocol in a 5 GHz frequency band for communication while connection between a relay node and a user may adopt IEEE 802.11b/g protocol in a 2.4 GHz frequency band for communication.
Operation of the current multi-hop wireless backhaul network still lacks an efficient medium access control (MAC) protocol. In general, the multi-hop wireless backhaul network usually adopts a chain network topology and communication between relay nodes uses the distributed coordination function (DCF) medium access control protocol defined by the IEEE 802.11 standard. However, the currently adopted IEEE 802.11 DCF medium access control protocol results in the poor transmission rate, the serious problem of unfair efficiency, and inability to guarantee service quality.